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Electrically driven cracks in piezoelectric ceramics: experiments and fracture mechanics analysis |
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| Authors: | SL dos Santos e LucatoH-A Bahr V-B PhamDC Lupascu H BalkeJ Rödel U Bahr |
| Institution: | a Darmstadt University of Technology, Institute of Materials Science, Ceramics Group, Petersenstr. 23, 64287 Darmstadt, Germany b Dresden University of Technology, Institute of Solid Mechanics, 01062 Dresden, Germany c Dresden University of Technology, Institute of Theoretical Physics, 01062 Dresden, Germany |
| Abstract: | Piezoelectric systems like multilayer actuators are susceptible to damage by crack propagation induced by strain incompatibilities. These can arise under electric fields for example between the electroded and external regions. Such incompatibilities have been realised in thin rectangular model specimens from PZT-piezoelectric ceramics with top and bottom electrodes only close to one edge. Under an electric field, controlled crack propagation has been observed in situ in an optical microscope. The crack paths are reproducible with very high accuracy. Small electrode widths lead to straight cracks with two transitions between stable and unstable crack growth regions, while large electrode widths result in curved cracks with four transitions. Fracture mechanics analysis is able to explain the different crack paths. An iteration method is developed to simulate the curved crack propagation also for strong curvature of the crack paths using the finite element method. The computed crack contours exhibit excellent quantitative agreement with the experiment with respect to their shape, the stages of stable and unstable crack propagation and the transitions between them. Finally, also the crack length as a function of the electric field can be predicted. |
| Keywords: | A Crack propagation and arrest A Delamination B Piezoelectric material B Strain compatibility C Finite elements |
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